say you have a sold (cone, sphere, cylinder, etc) and you want the flat shape, you need to set a section-slice through the object. For example; if you want the maximum rectangle from the cylinder, draw the section through the centre-point of the circle. Then take a 2D image of the cylinder if that is required. All the tools to do this are on the dashboard (Autocad 2008). Hint. put the UCS origin on the centre and point the y-axis to the centre-point of the opposite circular face. Then draw the slice. The tool can be gripped and dragged.